What I recall is that according to the Bible God created every plant, looked at his creation and declared it very good and then planted the Garden in Eden after the earth had brought forth all the plants. So your total nonsense idea of the most of the earth being inhospitable and plants and animals migrating out from Eden is not even Biblical.
Well, selective recall, I suppose is fine. But I prefer to look at the actual evidence, in this case, the text.
Gen 1:
11 And God said, Let the earth bring forth grass, [SIZE=-1][/SIZE]the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.
12 And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good.
13 And the evening and the morning were the
third day.
I do not see where it says every patch of planet earth there. I take it to refer to Eden, primarily, because, on this third day, that is where He planted the plants, far as I can tell. (Excepting some, it seems likely on the earth at large as well, that needed to be there, like some creatures, helping to get it more hospitable)
We can now look to the next chapter, where it was already finished, and go back for a close up of the plants issue, and how it was actually done.
1 Thus the heavens and the earth were
finished, and all the host of them.
8 And the LORD
God planted a garden eastward in Eden; and there he put the man whom he had formed.
9 And out of the ground made the LORD God to grow every tree that is pleasant to the sight, and good for food; the tree of life also
in the midst of the garden, and the tree of knowledge of good and evil.
You cannot prove from this, that ALL plants were planted all over the earth. That is the way God tells it.